Thanks for the reply.
German wines usually have the information you require on the front of the bottle.
The big supermarkets generally only have a fairly small number of German wines. (Many of their best wines, such as the 'new season' Rhine wines are generally only available in Germany. That means that the number of bottles that find their way onto the shelves of British supermarkets is fairly small). From your point of view that's probably a good thing because, once you've found the 'German white' section, you won't have to decide between a vast array of wines.
There might only be half a dozen or so German white wines on the shelves. Look for those bottles with 'Qualit�tswein mit Pr�dikat' - or 'QmP' - on the label. Then check that it's a Reisling or Gewurtztramminer. If you see 'Trockenbeerenauslese' (which is explained above) or just 'Beerenauslese' (which means that it's made from slightly over-ripe grapes, resulting in a slightly sweet wine) that will be just as good as seeing the name of one of those grape varieties.
Chris